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Zhuang H, Li Q, Sun C, Xu D, Gan G, Zhang C, Chen C, Yuan Y, Liu L, Xiao Y, Yao X, Wang C, Kang X, Yang C, Zhao J, Chen W, Wang J, Li J, Luo C, Wang J, Jia X, Yu Z, Liu L. Voluntary wheel exercise ameliorates cognitive impairment, hippocampal neurodegeneration and microglial abnormalities preceded by demyelination in a male mouse model of noise-induced hearing loss. Brain Behav Immun 2023; 114:325-348. [PMID: 37683962 DOI: 10.1016/j.bbi.2023.09.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 08/23/2023] [Accepted: 09/05/2023] [Indexed: 09/10/2023] Open
Abstract
Acquired peripheral hearing loss (APHL) in midlife has been identified as the greatest modifiable risk factor for dementia; however, the pathophysiological neural mechanisms linking APHL with an increased risk of dementia remain to be elucidated. Here, in an adult male mouse model of noise-induced hearing loss (NIHL), one of the most common forms of APHL, we demonstrated accelerated age-related cognitive decline and hippocampal neurodegeneration during a 6-month follow-up period, accompanied by progressive hippocampal microglial aberrations preceded by immediate-onset transient elevation in serum glucocorticoids and delayed-onset sustained myelin disruption in the hippocampus. Pretreatment with the glucocorticoid receptor antagonist RU486 before stressful noise exposure partially mitigated the early activation of hippocampal microglia, which were present at 7 days post noise exposure (7DPN), but had no impact on later microglial aberrations, hippocampal neurodegeneration, or cognitive decline exhibited at 1 month post noise exposure (1MPN). One month of voluntary wheel exercise following noise exposure barely affected either the hearing threshold shift or hippocampal myelin changes but effectively countered cognitive impairment and the decline in hippocampal neurogenesis in NIHL mice at 1MPN, paralleled by the normalization of microglial morphology, which coincided with a reduction in microglial myelin inclusions and a restoration of microglial hypoxia-inducible factor-1α (HIF1α) expression. Our results indicated that accelerated cognitive deterioration and hippocampal neuroplastic decline following NIHL are most likely driven by the maladaptive response of hippocampal microglia to myelin damage secondary to hearing loss, and we also demonstrated the potential of voluntary physical exercise as a promising and cost-effective strategy to alleviate the detrimental impact of APHL on cognitive function and thus curtail the high and continuously increasing global burden of dementia. Furthermore, the findings of the present study highlight the contribution of myelin debris overload to microglial malfunction and identify the microglial HIF1α-related pathway as an attractive candidate for future comprehensive investigation to obtain a more definitive picture of the underlying mechanisms linking APHL and dementia.
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Affiliation(s)
- Hong Zhuang
- Department of Physiology, School of Medicine, Southeast University, Nanjing 210009, China
| | - Qian Li
- Department of Physiology, School of Medicine, Southeast University, Nanjing 210009, China
| | - Congli Sun
- Department of Physiology, School of Medicine, Southeast University, Nanjing 210009, China
| | - Dan Xu
- School of Public Health, Southeast University, Nanjing 210009, China
| | - Guangming Gan
- School of Medicine, Southeast University, Nanjing 210009, China
| | - Chenchen Zhang
- School of Medicine, Southeast University, Nanjing 210009, China
| | - Chen Chen
- School of Medicine, Southeast University, Nanjing 210009, China
| | - Yang Yuan
- Department of Endocrinology, Zhongda Hospital, Medical School, Southeast University, Nanjing 210009, China
| | - Linchen Liu
- Department of Rheumatology, Zhongda Hospital, School of Medicine, Southeast University, Nanjing 210009, China
| | - Yu Xiao
- Department of Physiology, School of Medicine, Southeast University, Nanjing 210009, China
| | - Xiuting Yao
- Department of Physiology, School of Medicine, Southeast University, Nanjing 210009, China
| | - Conghui Wang
- Department of Physiology, School of Medicine, Southeast University, Nanjing 210009, China
| | - Xiaoming Kang
- School of Life Science and Technology, Southeast University, Nanjing 210009, China
| | - Chenxi Yang
- Department of Physiology, School of Medicine, Southeast University, Nanjing 210009, China
| | - Jingyi Zhao
- School of Life Science and Technology, Southeast University, Nanjing 210009, China
| | - Wenhao Chen
- School of Medicine, Southeast University, Nanjing 210009, China
| | - Jiatang Wang
- School of Medicine, Southeast University, Nanjing 210009, China
| | - Jinyu Li
- School of Medicine, Southeast University, Nanjing 210009, China
| | - Caichen Luo
- School of Medicine, Southeast University, Nanjing 210009, China
| | - Jie Wang
- School of Medicine, Southeast University, Nanjing 210009, China
| | - Xirui Jia
- School of Life Science and Technology, Southeast University, Nanjing 210009, China
| | - Zhehao Yu
- Department of Physiology, School of Medicine, Southeast University, Nanjing 210009, China
| | - Lijie Liu
- Jiangsu Provincial Key Laboratory of Critical Care Medicine, Department of Physiology, School of Medicine, Southeast University, Nanjing 210009, China.
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Azeem A, Julleekeea A, Knight B, Sohail I, Bruyns-Haylett M, Sastre M. Hearing loss and its link to cognitive impairment and dementia. FRONTIERS IN DEMENTIA 2023; 2:1199319. [PMID: 39081997 PMCID: PMC11285555 DOI: 10.3389/frdem.2023.1199319] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Accepted: 05/26/2023] [Indexed: 08/02/2024]
Abstract
Hearing loss is an important risk factor for the development of dementia, particularly Alzheimer's disease (AD). Mid-life hearing loss increases the risk of developing dementia by double any other single factor. However, given this strong connection between hearing loss and AD, the mechanisms responsible for this link are still unknown. Data from observational studies relating hearing loss and cognitive impairment, measured with standardized questionnaires, has shown a strong relationship between them. Similar findings have emerged from animal studies, showing that the induction of hearing loss via prolonged loud sound exposure or ear canal blocking, can impair cognitive abilities. Interestingly, patients with age-related hearing impairment exhibit increased phosphorylated tau in the cerebrospinal fluid, but no such relationship has been identified for amyloid-β. In addition, hearing loss predisposes to social isolation precipitating the development of dementia through a supposed reduction in cognitive load and processing requirements. Given this link between hearing loss and dementia, the question arises whether the restoration of hearing might mitigate against the onset or progress of AD. Indeed, there is a growing body of research that suggests that those who wear hearing aids for age-related hearing problems maintain better cognitive function over time than those who do not. These are compelling findings, as they suggest the use of hearing aids has the potential to be a cost-effective treatment for those with hearing loss both prior (for those at high risk for AD) and after the development of symptoms. This review aims to summarize the current theories that relate hearing loss and cognitive decline, present the key findings of animal studies, observational studies and summarize the gaps and limitations that need to be addressed in this topic. Through this, we suggest directions for future studies to tackle the lack of adequately randomized control trials in the field. This omission is responsible for the inability to provide a conclusive verdict on whether to use hearing interventions to target hearing-loss related cognitive decline.
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Affiliation(s)
- Abdul Azeem
- Department of Brain Sciences, Imperial College London, London, United Kingdom
| | - Arun Julleekeea
- Department of Brain Sciences, Imperial College London, London, United Kingdom
| | - Beth Knight
- Department of Brain Sciences, Imperial College London, London, United Kingdom
| | - Isha Sohail
- Department of Brain Sciences, Imperial College London, London, United Kingdom
| | | | - Magdalena Sastre
- Department of Brain Sciences, Imperial College London, London, United Kingdom
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Kurioka T, Mizutari K, Satoh Y, Shiotani A. Correlation of blast-induced tympanic membrane perforation with peripheral cochlear synaptopathy. J Neurotrauma 2022; 39:999-1009. [PMID: 35243914 DOI: 10.1089/neu.2021.0487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The auditory organs, including the tympanic membrane, cochlea, and central auditory pathway, are the most fragile components of the human body when exposed to blast overpressure. Tympanic membrane perforation (TMP) is the most frequent symptom in blast-exposed patients. However, the impact of TMP on the inner ear and central auditory system is not fully understood. We aimed to analyze the effect of blast-induced TMP on the auditory pathophysiological changes in mice after blast exposure. Mice aged 7 weeks were exposed to blast overpressure to induce TMP and allowed to survive for 2 months. All TMP cases had spontaneously healed by week 3 following the blast exposure. Compared to controls, blast-exposed mice exhibited a significant elevation in hearing thresholds and an apparent disruption of stereocilia in the outer hair cells, regardless of the occurrence or absence of TMP. The reduction in synapses in the inner hair cells, which is known as the most frequent pathology in blast-exposed cochleae, was significantly more severe in mice without TMP. However, a decrease in the number of excitatory central synapses labeled by VGLUT-1 in the cochlear nucleus was observed regardless of the absence or presence of TMP. Our findings suggest that blast-induced TMP mitigates peripheral cochlear synaptic disruption but leaves the central auditory synapses unaffected, indicating that central synaptic disruption is independent of TMP and peripheral cochlear synaptic disruption. Synaptic deterioration in the peripheral and central auditory systems can contribute to the promotion of blast-induced hearing impairment, including abnormal auditory perception.
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Affiliation(s)
- Takaomi Kurioka
- Department of Otolaryngology, Head and Neck Surgery and National Defense Medical College, Saitama, Japan
| | - Kunio Mizutari
- Department of Otolaryngology, Head and Neck Surgery and National Defense Medical College, Saitama, Japan
| | - Yasushi Satoh
- Department of Biochemistry, National Defense Medical College, Saitama, Japan
| | - Akihiro Shiotani
- Department of Otolaryngology, Head and Neck Surgery and National Defense Medical College, Saitama, Japan
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Conductive hearing loss during development does not appreciably alter the sharpness of cochlear tuning. Sci Rep 2021; 11:3955. [PMID: 33597563 PMCID: PMC7890061 DOI: 10.1038/s41598-021-83115-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 01/22/2021] [Indexed: 02/02/2023] Open
Abstract
An increasing number of studies show that listeners often have difficulty hearing in situations with background noise, despite normal tuning curves in quiet. One potential source of this difficulty could be sensorineural changes in the auditory periphery (the ear). Signal in noise detection deficits also arise in animals raised with developmental conductive hearing loss (CHL), a manipulation that induces acoustic attenuation to model how sound deprivation changes the central auditory system. This model attributes perceptual deficits to central changes by assuming that CHL does not affect sensorineural elements in the periphery that could raise masked thresholds. However, because of efferent feedback, altering the auditory system could affect cochlear elements. Indeed, recent studies show that adult-onset CHL can cause cochlear synapse loss, potentially calling into question the assumption of an intact periphery in early-onset CHL. To resolve this issue, we tested the long-term peripheral effects of CHL via developmental bilateral malleus displacement. Using forward masking tuning curves, we compared peripheral tuning in animals raised with CHL vs age-matched controls. Using compound action potential measurements from the round window, we assessed inner hair cell synapse integrity. Results indicate that developmental CHL can cause minor synaptopathy. However, developmental CHL does not appreciably alter peripheral frequency tuning.
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Decreasing auditory input induces neurogenesis impairment in the hippocampus. Sci Rep 2021; 11:423. [PMID: 33432038 PMCID: PMC7801596 DOI: 10.1038/s41598-020-80218-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 12/07/2020] [Indexed: 02/06/2023] Open
Abstract
Hearing loss is associated with cognitive decline and dementia risk. Sensorineural hearing loss suppresses hippocampal neurogenesis, resulting in cognitive decline. However, the underlying mechanism of impaired neurogenesis and the role of microglial activation and stress responses related to hearing loss in the hippocampus remains unknown. Using a conductive hearing loss (CHL) model, we investigated whether a decrease in sound level could induce impairment of hippocampal neurogenesis and examined the differences between unilateral CHL (uCHL) and bilateral CHL (bCHL). To establish the CHL mouse model, ears were unilaterally or bilaterally occluded for five weeks by auditory canal ligation. Although hearing thresholds were significantly increased following CHL, CHL mice exhibited no significant loss of spiral ganglion or hippocampal neurons. Hippocampal neurogenesis was significantly and equally decreased in both sides following uCHL. More severe decreases in hippocampal neurogenesis were observed in both sides in bCHL mice compared with that in uCHL mice. Furthermore, microglial invasion significantly increased following CHL. Serum cortisol levels, which indicate stress response, significantly increased following bCHL. Therefore, auditory deprivation could lead to increased microglial invasion and stress responses and might be a risk factor for hippocampal neurogenesis impairment.
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Kurioka T, Sano H, Furuki S, Yamashita T. Long-term administration of vitamin B12 and adenosine triphosphate for idiopathic sudden sensorineural hearing loss: a retrospective study. PeerJ 2020; 8:e10406. [PMID: 33362960 PMCID: PMC7749652 DOI: 10.7717/peerj.10406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 10/31/2020] [Indexed: 11/24/2022] Open
Abstract
Background In idiopathic sudden sensorineural hearing loss (ISSNHL), the relationship between the administration duration of vitamin B12 (vit B12) with adenosine triphosphate (ATP) and their therapeutic effect is not fully understood. Objective To investigate the therapeutic effect of long-term 16 (≥weeks) administration of vit B12 with ATP on the prognosis of ISSNHL patients and compare it with those of short-term (<8 weeks) and middle-term (≥8 weeks, <16 weeks) administration. Methods We retrospectively reviewed the medical records of 117 patients with ISSNHL treated between 2015 and 2018. Results The overall recovery rate was 32.5%. Initial higher hearing threshold and initial higher grade of hearing loss (HL) were associated with a poor prognosis. However, the administration duration of vit B12 and ATP did not influence the overall hearing improvement. With regard to the time course of hearing recovery, there was no significant difference in hearing recovery among the long-, middle-, and short-term administration groups until 16 weeks after treatment. However, at 16–24 weeks after initial treatment, the short-term administration group exhibited significantly lower hearing recovery than did the long-term administration groups. Conclusions The administration duration of vit B12 and ATP did not influence the overall hearing prognosis in ISSNHL, but long-term administration of vit B12 and ATP helped prevent the progression of HL after ISSNHL. Our results suggest that long-term administration of vit B12 and ATP is not necessarily required to treat ISSNHL patients, except for slowly progressing HL in the affected ears.
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Affiliation(s)
- Takaomi Kurioka
- Department of Otorhinolaryngology, Head and Neck Surgery, Kitasato University, Kanagawa, Japan
| | - Hajime Sano
- School of Allied Health Sciences, Kitasato University, Kanagawa, Japan
| | - Shogo Furuki
- Department of Otorhinolaryngology, Head and Neck Surgery, Kitasato University, Kanagawa, Japan
| | - Taku Yamashita
- Department of Otorhinolaryngology, Head and Neck Surgery, Kitasato University, Kanagawa, Japan
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Transient Conductive Hearing Loss Regulates Cross-Modal VGLUT Expression in the Cochlear Nucleus of C57BL/6 Mice. Brain Sci 2020; 10:brainsci10050260. [PMID: 32365514 PMCID: PMC7287693 DOI: 10.3390/brainsci10050260] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Revised: 04/27/2020] [Accepted: 04/29/2020] [Indexed: 12/19/2022] Open
Abstract
Auditory nerve fibers synapse onto the cochlear nucleus (CN) and are labeled using the vesicular glutamate transporter-1 (VGLUT-1), whereas non-auditory inputs are labeled using the VGLUT-2. However, the underlying regulatory mechanism of VGLUT expression in the CN remains unknown. We examined whether a sound level decrease, without primary neural damage, induces cellular and VGLUT expression change in the CN, and examined the potential for neural plasticity of the CN using unilateral conductive hearing loss models. We inserted earplugs in 8-week-old mice unilaterally for 4 weeks and subsequently removed them for another 4 weeks. Although the threshold of an auditory brainstem response significantly increased across all tested frequencies following earplug insertion, it completely recovered after earplug removal. Auditory deprivation had no significant impact on spiral ganglion and ventral CN (VCN) neurons’ survival. Conversely, although the cell size and VGLUT-1 expression in the VCN significantly decreased after earplug insertion, VGLUT-2 expression in the granule cell lamina significantly increased. These cell sizes decreased and the alterations in VGLUT-1 and -2 expression almost completely recovered at 1 month after earplug removal. Our results suggested that the cell size and VGLUT expression in the CN have a neuroplasticity capacity, which is regulated by increases and decreases in sound levels. Restoration of the sound levels might partly prevent cell size decrease and maintain VGLUT expression in the CN.
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